Whiskers have attracted increasing interest from engineers seeking to imitate their numerous desirable sensing properties. Whiskers are physically robust, mechanically simple, and yet can precisely extract object shape, texture and the velocity of fluid flow. The diverse capabilities of whiskers are amply demonstrated by the animals that use them to perform difficult behavioral tasks. Robotic whiskers have been used for various types of sensing tasks (for a detailed review), and several recent studies have specifically addressed the issue of three-dimensional (3-D) feature extraction, wherein the goal is to infer the shape of an object by repeated contact with one or more whiskers. These studies have generally taken one of two approaches: whisker “tapping” or whisker “sweeping.”
Whisker tapping involves rotating or translating the whisker(s) against an object by a small angle and inferring where along the length of the whisker initial contact occurred (i.e., radial distance extraction). Using this information, along with information about the angle of initial contact and location of the whisker base, allows estimation of the contact point location in 3-D space for each whisker.
Whisker sweeping involves moving the whisker along or against the object far past the location of initial contact in order to estimate a collection of contact point locations as the whisker slips along the surface.